Short answers, pulled from the story.
Robert Oppenheimer demonstrated that the equations governing the interaction between light and electrons produced infinite results in 1930. This mathematical catastrophe threatened to destroy the entire field of theoretical physics for two decades.
Carl David Anderson discovered the positron in cosmic rays in 1932. This discovery confirmed that antimatter was a real component of the universe and fundamentally changed the understanding of particle physics.
The Higgs boson was detected at CERN in 2012. This detection validated the existence of all constituents of the Standard Model and confirmed the electroweak interaction theory.
Freeman Dyson proved that the renormalization procedure could only be applied to a small class of theories in 1951. This proof left many theories, including the Fermi theory of the weak interaction, as non-renormalizable.
Steven Weinberg combined gauge theory with the mechanism of spontaneous symmetry breaking in 1967. This theory predicted that the W and Z bosons acquire mass through the Higgs mechanism while the photon remains massless.